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Hybodus
Hybodus is a genus of prehistoric shark in the order Hybodontiformes. The name Hybodus means "humped tooth". This genus of shark is known for its distinctive dorsal spikes rising in front of both of its dorsal fins. Fossil evidence indicates Hybodus ''first appeared appeared in the Permian and only disappeared during the Late Cretaceous. Its apparent extinction occurred slightly before the K-Pg Extinction, and the reason why it died out is not certain. Description The various ''Hybodus species grew to about 2 metres (6.6 ft) in length, and are believed to have been opportunist predators. It was not a very large shark (perhaps no larger than the modern Grey reef shark in size), but had the classic streamlined shark shape, complete with two dorsal fins that would have helped it steer with precision. The mouth was not large, and rather than ruthlessly hunt large prey, Hybodus, was capable of eating a wide range of foods. They had several distinct features that made them stand apart from other primitive sharks. Firstly, they had two different types of teeth, suggesting a highly varied diet. The teeth of Hybodus are highly specialized. Its front teeth appear to be sharper, more useful for gripping fish or cephalopods, while the back teeth appear to be more rounded, which seem to be more suited to crushing the shells of clams and crustaceans. This heterodont tooth morphology is seen today in bamboo sharks, which can flatten their teeth into crushing plates and raise their teeth to target and capture fish and cephalopods. Secondly, they had a bony blade on their dorsal fin that probably served a defensive function, much like in modern dogfish and bullhead sharks. The males also possessed claspers, specialized organs that directly insert sperm into the female, which are still present in modern sharks. The horns on the heads of the males may have been used in helping maintain a grip on females during mating. Most shark fossils are not very complete due to the fact that sharks have cartilaginous skeletons. However, Hybodus' cartilage appears to be highly ossified, meaning that people know far more about the morphology of this animal than most prehistoric sharks. The youngest Hybodus fossils come from the Dinosaur Park Formation in Alberta, Canada. They date from 68.6 to 66 million years ago, in the Maastrichtian Stage. The first fossilized teeth from Hybodus were found in England around 1845. Since then, teeth and dorsal spines from this genus of shark have been recovered from around the world. In Popular Culture Hybodus was featured in the third episode of the 1999 documentary series Walking with Dinosaurs, being attracted to the blood of an Ophthalmosaurus in labor. It was unidentified in the UK version. Hybodus made its return in the 2003 spin-off Sea Monsters, where it was shown feeding on a giant struggling Leedsichthys with the marine crocodile Metriorhynchus. In 2004, the children's book Jurassic Shark by Deborah Diffily (illustrated by Karen Carr) highlights a pregnant female Hybodus ''shark battling a ''Liopleurodon and hunting ichthyosaurs.Category:Prehistoric Sharks Category:Chondrichthyes Category:Elasmobranchs Category:Sharks Category:Extinct Species Category:Hybodontiformes